Conventionally, when an affected part (i.e., lesion area) of a patient is irradiated with radioactive rays as treatment, the affected part moves in some cases due to movement of the patient such as breathing, heartbeat, and/or intestinal movement. Thus, the affected part is irradiated with radioactive rays under a gated irradiation method using a metal marker or a tracking irradiation method. For instance, by imaging a patient with the use of X-rays during treatment, a fluoroscopic image depicting the marker placed in the vicinity of the affected part is obtained. The movement of the marker is tracked by matching the fluoroscopic image with a template such that the affected part is irradiated at an appropriate timing.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2000-167072
In the above-described technique, a user such as a doctor and/or a radiological technician has to set the template while referring to the fluoroscopic image of the patient whose X-ray images are preliminarily generated during treatment planning, which takes time and effort. Further, when the entire range of the fluoroscopic image is processed on a real-time basis in the case of tracking the position of the marker by performing image processing on the fluoroscopic image during treatment, processing load of the CPU increases. Thus, a user has to previously set the range in which the marker is depicted in the fluoroscopic image in order to reduce the load of image processing, and there is a problem that it takes time and effort.